"张开嘴" 用英语可以说作 "open one's mouth" 或者 "part one's lips." 这两种表达都指的是张开嘴巴的动作。"Open one's mouth" 是由动词 "open" 和介词短语 "one's mouth" 拼接而成，"open" 意思是 "开"，"one's mouth" 意思是 "某人的嘴巴"。"Part one's lips" 则是由动词 "part" 和名词短语 "one's lips" 组成，"part" 的意思是 "分开"，"one's lips" 意思是 "某人的嘴唇"。

下面是一些英文例句：

Open your mouth and say "ahh" so I can check your tonsils.

打开你的嘴巴，说一声 "啊"，这样我就可以检查你的扁桃体了。

She parted her lips and blew a kiss to her boyfriend.

她张开嘴唇，向男友吹了个飞吻。

The baby opened its mouth wide and cried for food.

婴儿张开嘴巴哭着要吃东西。

He parted his lips slightly and whispered something in her ear.

他微微地张开嘴唇，在她耳边低声说了些什么。